The single most important factor related to children's academic achievement is the number of books they have in their home.

By Eryk Bagshaw

On Tuesday morning more than 600,000 primary students in NSW will pack their lunch boxes, pop on their uniforms and walk through the gates of school for the first day of term.

For almost 40 per cent of them their parents will be paying for another term of hefty fees to cover the cost of a private education, but a new study published in the Australian Journal of Labour Economics could leave many of them wondering if that new blue blazer is really worth it.

The findings into the largest longitudinal study of 4000 private primary and public school students in Australian history were released by researchers this week.Credit:Louie Douvis

This week, researchers at the University of Queensland's Faculty of Health and Behavioural Sciences released their findings into the largest longitudinal study of 4000 private primary and public school students in Australian history.

The data tracked children from the age of four to ten and included metrics on Naplan results, variations on IQ tests and non-cognitive outcomes such how they interact with peers.

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The report's author, Luke Connelly, said the data allowed for a unique form of thought experiment.

"Imagine somebody you know who is quite successful then think about whether they went to a public or private school. Now consider whether they were already destined to be successful."

"The question is: does the type of school create any additional advantage?"

Not according to the research.

Professor Connelly and his team found that sending children to Catholic or other independent primary schools has "no significant effect" on any of these outcomes.

A far more important factor, the report argues, is the background of the child's family, including income, social circles, the number of people who had completed high school in their neighbourhood, their parents educational attainment or health factors, such as the weight of a baby at birth.

But there is one key factor to rule them all. "Children in families with more books at home have consistently higher test scores," he said.

Those books can prove their worth long before the child scribbles down their first word.

"One of the strongest predictors of a child's success is their level of development at preschool. What the data suggests is that because they haven't been exposed to schooling yet, whatever skills that have been developed due to nature or nurture are really influential."

The results from the Australia-wide study match those in the comparative education systems of the United States and Britain which found no academic benefit to attending either Catholic or independent primary schools. Like Professor Connelly, the authors of a report in the Journal of Political Economy on those countries found that extraneous circumstances were a much better predictor of success.

The University of Queensland's research is limited in that it does not take into account high school data, when swaths of parents move their children out of public education and into private secondary schools. Professor Donnelly hopes that by 2018 the same set will track students taking the Naplan in year 9.

Public schooling advocates have latched onto the report since its release to demand that all state governments fully commit to the Gonski public funding reforms. In March, the NSW government warned that the "most significant education reform in 40 years" is under threat after the Victorian government refused to commit to the final two years.

Save Our Schools spokesman Trevor Cobbold said the report confirmed more funding needed to be redirected to public schools.

"The findings of these studies send a simple message for parents who send their children to private schools. If you think you are getting some advantage in education outcomes from sending your child to a private school rather than a government school, think again".

Despite the research, non-government school enrolments are growing, rapidly. A Productivity Commission report released in February showed a 10 per cent surge in combined enrolments for primary and high school students, while total government funding per student for NSW public school students rose by 8 per cent over the past decade, compared with 12 per cent for private schools.

Dr Geoff Newcombe, executive director of the Association of Independent Schools of NSW, dismissed the value of the study as "questionable."

"Parents choose an independent school for a wide variety of reasons including its values and ethos, focus on pastoral care and extracurricular options, as well as academic rigour," Dr Newcombe said. "The strong enrolment growth we see in the sector is testament to the fact that independent schools are meeting parents' expectations by providing high-quality teaching and learning.

"As the study points out, a range of other factors are key to a student's achievement and I think we would do well to focus more on these and seek to replicate the positives across our entire education system in all schools."

So no matter what classroom your child finds themselves in, what is the key to statistical success?

Hope that they weigh more than 2.5 kilograms when they are born into a wealthy neighbourhood where the majority of people have finished high school and everyone buys them lots and lots of books.